The invention relates to a resealable pouring spout for a bag consisting of flexible film.
This particular resealable pouring spout is in the form of one of the variants comprising a built-in cutting device, which variants are nowadays being used increasingly frequently. As is known, built-in cutting devices are so frequently used because a very large demand for easily producible containers which meet the hygiene conditions and are eco-friendly is fundamentally needed for the storage and transport of easily perishable goods such as foods, and because self-evidently, with wholly closed bags, the integrity of which is first in any way destroyed, by being cut open, only when used for the first time, the required standards with respect to freshness and sterility can be most likely guaranteed.
A resealable pouring spout of this type, for a bag consisting of flexible film, here consists of a pouring spout body, which can be welded to the bag and has a flange, a cutting device disposed in the pouring spout body and having a flange-side cutting system, and a screwable sealing cap placed onto the pouring spout body. The sealing cap is here provided with means in the form of drivers in order to move the cutting device in the direction of the flange when the sealing cap is opened for the first time, and thereby cut open the bag in the flange region and create a pour-out opening there. Although resealable pouring spouts of this type are known per se, they have the drawback that the currently known forms often fail to work wholly satisfactorily if they are welded directly onto the flexible film material of a tubular plastics bag. This has to do with the physical properties of the film material.
The problem stems namely from the fact that the hitherto used cutting devices are incompatible with some physical properties of the film material of which the bags consist, because, when the bags are pierced and cut open, effects in fact arise, which, in the opening of the container, are extremely undesirable.
If, namely, it is attempted to circularly cut open a flexible film in a known manner with a previously described cutting device and thus create a pour-out opening, it will be discovered that, although the flexible film can be pierced relatively easily, upon further turning of the sealing cap the cutting torque forces acting on already elastically deformed film increase with such rapidity that the flexible film can no longer withstand the torsional and shearing forces and tears uncontrollably. This leads to a situation in which not only is the further unscrewing of the screw cap, which for its part is obviously coupled with the cutting device, made much more difficult, but also, because of the uncontrollable tearing, no clearly defined pour-out opening whatsoever is formed, so that consequently the actual pouring out is also then heavily impaired. The case will namely frequently arise that film tabs which have been uncontrollably torn partially reclose the formed pour-out opening in the course of the pouring out. In somewhat simple terms, the problem could thus be paraphrased with the following analogy: it resembles the attempt to cut up a loosely held rubber band with a plastics knife.
This problem has, of course, been recognized. For reasons of resource-sparing material consumption, but also for reasons of transport security, it is nevertheless very sensible, of course, to use bags consisting of flexible film. If it is namely wished to achieve a situation in which flexible containers also survive dropping from different heights without damage, then care must be taken to ensure that the material used is flexible enough, since it would otherwise not in fact be able to absorb the impact energy and would burst.
One of the solutions for use in flexible containers is disclosed in EP-1 396 435. Although this publication describes a resealable pouring spout for a bag consisting of flexible material, it is here a case of a composite material comprising plastics and paper layers, so that in terms of its cutting-open characteristics, in particular, of course, owing to its higher basic stiffness, it has totally different properties than might be expected in a tubular bag consisting of pure plastics material. All the same, this cutting device does however have a structure comprising a plurality of cutting tooth groups, which are arranged distributed over a cutting circle circumference and protrude on a continually decreasing scale less far than a leading cutting tooth. With this arrangement, the cutting open is meant to be realized not solely by the leading cutting tooth, for it is wished to avoid, as far as possible, horizontal warping of the composite material.
A further solution is shown in WO2011/039504. This publication describes a resealable pouring spout for a bag consisting of plastics film material, i.e. for an actual tubular bag (pouch). The cutting device contained in this pouring spout has a structure comprising a plurality of cutting tooth groups, which are arranged distributed over a cutting circle circumference and the individual cutting teeth of which protrude continually less far in comparison to two respectively leading (forward or trailing) cutting teeth. Both the leading cutting teeth and the follow-up teeth, which latter are stepped at different heights, of the stepping tooth groups are all configured such that they taper to a point and are all designed for stock-removing cutting effect. In this cutting device, in the course of use, one after the other of the follow-up teeth is employed, according to the penetration depth. In this cutting device, too, it is naturally a question of as far as possible avoiding, or at least minimizing, the effect, which arises still more markedly in pure plastics film material, of horizontal warping, or even uncontrolled tearing, of the film material as it is cut open.
In bags consisting of flexible film, precisely owing to the low stiffness of the plastics film material, cutting systems, i.e. systems of actual cutting teeth, have the drawback that a clean cut—once the starting cut or the penetration is realized—can subsequently be maintained only with even greater difficulty. As already mentioned, this has to do with the fact that the material to be cut through would have to remain taut for as long as possible in order to obtain a clean cut.